This invention relates generally to a latching device for railway car doors, and more particularly to such a device as having a hasp latched against vertical upward movement by a pair of cams regardless of the forces to which the device is subjected tending to cause the cams to rotate out of a latching position.
U.S. Pat. No. 3,933,384 to Schuller et al relates to an anti-pilferage locking device including a hasp used for latching a longitudinally sliding member in place against a stationary frame structure, the hasp being mounted on the door and being engageable with a flange provided on a keeper mounted on the bracket located on the frame structure. A single cam element is mounted on the keeper for pivotal movement above the hasp, and has a flat lower horizontal edge engageable with an edge of the hasp so as to limit vertical movement thereof. Locking means may also be provided for locking the cam and hasp in place.
The disadvantage with such an arrangement is that the cam element, when serving as a latch without the lock means being used, may easily unlatch and permit disengagement of the hasp upon an application of a force tending to pivot the cam away from the hasp. Such a force may occur as a result of impact between adjoining railway cars. And, if the cam is pivoted out of its latching position, a vertical impact could easily disengage the hasp from the keeper. A need therefore arises to avoid inadvertent unlatching of the device in the presence of normal forces to which the railway car is subjected, and also to render the device more difficult to unlatch by unauthorized personnel.